1) Roof works ... noticable changes in the gadgetery etc in the boot
2) Engine is much much quiter and smoother
3) Fuel economy is better
4) Leather is better quality
5) Seats are more supportive
6) Gearchange is slicker
7) Stereo is better
9) Handling is sharper
10) Brakes actually work properly in the wet
11) Generally much less road noise
Basically it seems that Peugeot have been doing quite a lot of listening to people and really have improved the car, as it needed to be.
Best advice to anyone is get rid of your 2001 models now ... and if you are thinking of buying one second hand .. don't ... it really is worth paying the extra money for a new one.
Contented (at last) CC owner